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Technical Section
How is the user’s power measured by the Spinner Blade ION?
The system measures the tangential (cross directional) force the brake pad applies to the Spinner Blade ION flywheel through a load cell.
Knowing the tangential force component, the resulting restive torque, and the rider’s cadence, allows the computer to provide an accurate
rider power output. Watts is a measure of the rider’s force sustained over a set distance and time. The Spinner Blade ION determines the
rider’s Watts, by measuring the force at the flywheel with a load sensor. By monitoring the rider’s cadence at these loads, the computer can
determine the rider’s power. Unlike a geared road bike where measurement at the crank is the optimal location, measurement on a fixed
gear group cycle is best measured exactly where the work is being applied. As our riders become stronger, they will find they are able to
sustain higher average watts through their ride, as well as higher interval watts during sprints.
How does this compare to actual road bike power measurement from companies like SRM and Power Tap?
The best cycling power measurement systems use strain gauges to measure the reciprocating crank load cycles at a measurement point on
the bike; the predominate measurement points are located at the crank, the cassette or the pedal. The computer then takes these
reciprocating loads and their angular speeds, and calculates / averages the power output with mathematical formulas.
How do we validate the accuracy of the Spinner Blade ION strain gauge technology?
We validate the accuracy through a comparison test, by measuring the difference between the input power to drive the bike compared to
the resulting power output measured by the computer. We apply input power through a motor coupled to the crank, with a measurement
device called a Dynamometer. The Dynamometer offers measurements with 99.5% accuracy (0.5% error). We compare this power input to
the computer’s measured power output. By knowing the difference between the dynamometer power input and watts computer power
output we can validate the accuracy of the system. The Spinner Blade ION is generally better than 5% of true watts values measured at the
Dynamometer, and in off nominal cases within 10% of true watts values measured. When we get more bikes in we likely will want to
conduct a study, and come up with our claims that are backed by a larger data set.
With no visible cadences sensor on the flywheel or crank arm, how is cadence measured and how does this correlate to distance?
The Spinner Blade ION develops its own electric power through a generator. The computer monitors the generated power, and can
determine the precise speed of the system based on the electrical pulses generated in the system. These pulses correlate to the rider’s
cadence. The computer looks at the flywheel RPM and does two conversions – one conversion converts RPM into crank cadence and the
other into rolling distance. The net result is a precise measurement of pedal cadence and the other is the rolling total distance of the
flywheel calculated.
Does the Spinner Blade ION require calibration at install or after use as part of preventative maintenance?
The Spinner Blade ION bike does not require calibration at install or as part of a preventative maintenance cycle. The load cell has a
predictable load curve that is set during manufacturing, and does not drift or migrate to require recalibration. The Spinner Blade ION sensor
is calibrated at the factory to deliver specific electrical output at given load points during the manufacture process. These points do not drift
or change over time, resulting in consistent readings through the life of the sensor.
The system incorporates a permanent magnet generator system. As the rider inputs mechanical energy into the pedals, the flywheel and a
set of magnets rotate in close proximity to a stator filled with copper windings. The magnetic flux of the rotating magnets about the stator
causes electromagnetic induction, creating a low power energy source to operate the computer and load cell.
SPINNER BLADE ION MANUFACTURED by STAR TRAC - OWNER’S MANUAL |
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